Maybe I'm just unlucky, but I've encountered several more: One Last Night, My Brother's Keeper (notable for being one of the first Shining Armor fanfics), Like Two Peas In a Pod, Big Brother Best Friend. Forever. and Vindicated Depravity (debatable, as it's Cadance dressing up as Twilight, but I still count it). Granted, five isn't exactly a lot but it's four more then I've wanted to see (My Brother's Keeper is actually a pretty funny crackfic).

Imagine a freight train roaring down the tracks. Everything's going fine. And then the tracks further along are torn apart like a child's plaything. That is what you just did to my assumption of the direction of this story.